Various electronic devices are mounted on a motor vehicle as a mobile unit. Therefore, the motor vehicle is provided with a wiring harness for transmitting power from a power source and control signals from a computer to the electronic devices. The wiring harness includes a plurality of electric wires and connectors attached to an end of the wires.
The wire includes an electrically conductive core wire and a coating made of insulating synthetic resin, which coats the core wire. The wire is a so-called coated wire. A connector includes an electrically conductive terminal fitting and an electrically insulating connector housing. The terminal fitting is attached to an end of the wire and electrically connected to the core wire of the wire. The connector housing is formed in a box-shape and receives the terminal fitting therein.
When the wiring harness is assembled, first the wire is cut into a specific length and then the terminal fitting is attached to an end of the wire. A wire is connected to another wire according to the need. Afterward, the terminal fitting is inserted into the connector housing, thereby assembling the wiring harness.
The wire of the wiring harness must be distinguished in terms of the size of the core wire, the material of the coating (concerning with alteration in the materials depending upon heat-resisting property), and a purpose of use. The purpose of use means, for example, an air bag, antilock brake system (ABS), control signal such as speed data, and system in a motor vehicle in which the wire is used, such as a power transmission system.
So far, in order to distinguish the purpose of use (or system) as described above, for example, an outer surface of the electric wire of the wiring harness is formed to have a stripe pattern with two different colors. In this case, when the coating is formed by extruding synthetic resin onto the periphery of the core wire so as to coat the core wire, first a coloring agent having a desired color is mixed into the synthetic resin that constitutes the coating. Then, another coloring agent having a color different from that of said desired color is applied on the synthetic resin (i.e. on a part of the outer surface of the coating). Thus, the part of the outer surface of the coating is colored so as to color the electric wire in a stripe pattern.
Generally, a motor vehicle is used for a long period of time from several years to more than ten years. Further, a motor vehicle may be used in various regions such as very cold regions or very hot regions. Therefore, if the electric wire used in a motor vehicle is colored in a stripe pattern, the coloring agent, particularly the coloring agent which is applied later, tends to come off from the outer surface of the electric wire as time passes.
Further, since the motor vehicle is used for a long period of time as described above, it happens that a new electronic instrument is added thereinto during use. Therefore, if the coloring agent comes off from the outer surface of the electric wire, it becomes difficult to distinguish the electric wires from one another, resulting in that it becomes difficult to electrically connect the additional electric instrument to a desired electric wire. That is, it is demanded that the color of the outer surface of the electric wire used in a motor vehicle does not come off in severe circumstances for a long period of time.
It is therefore an objective of the present invention to provide an electric wire, in which a color of the outer surface of the electric wire is securely prevented from coming off.